1. Field of the Invention
The invention relates to the production of photoimages by a process adaptable to a wide variety of graphic arts applications and which comprises the production of developable latent images in a polymeric substrate by the direct photooxidation of organic sulfide containing functional groups in the polymer. The invention is also directed to the sulfur containing polymer film materials per se.
2. Description of the Prior Art
The photoimaging of polymeric films by selective exposure to irradiation to effect localized cross-linking or curing is well known. The mechanism involved frequently depend upon polymerization or cross-linking which is initiated by free radicals and which requires the presence of a peroxide or other source of free radicals. The exposed regions of the polymer film are generally rendered relatively insoluble when compared with the unexposed regions thus providing a latent image which may be developed by washing with a suitable solvent.
Photooxidative processes for imaging polymer films have been described in a number of issued U.S. Pat., e.g., Nos. 3,790,389, Heimsch et al; 3,801,320, Erickson; 3,847,609 and 3,926,642 both issued to Breslow et al, and 3,846,266, Duynstee et al. These processes achieve photoimaging by the photooxidation of ##STR1## unsaturation in polymer films by exposure in the presence of oxygen and a photosensitizer. The photooxidation results in the production of hydroperoxides attached to the polymer chain at the site of the allylic unsaturation. The latent hydroperoxide polymer image may then be amplified and/or developed by a variety of techniques. The present invention does not depend for imaging upon the hydroperoxidation of ##STR2## unsaturation, but the speed of the film is enhanced by the further presence of ##STR3## unsaturation in the polymer substrate. In film embodiments where higher speed is a desirable property the co-presence of photooxidizable sulfur functionality with ##STR4## unsaturation constitutes a preferred embodiment of the invention.